This really excellent piece (http://www.chronicle.com/article/We-Know-What-Works-in-Teaching/238792/) lists the current best practices in the teaching of writing--all practices that I use with my coaching clients.
Here's the tl;dr version:
* Work with the process (research, draft, revise [a lot], revise some more, edit)
* Slowly ramp up the complexity of your writing tasks, both in the steps you take to produce a particular manuscript and in the complexity of the writing projects you take on. (This is why many graduate students are asked, for example, to write an annotated bibliography before they write a lit review. It ensures that you've finished the research and it's a simple, familiar summarization task; lit reviews are synthetic and are a much more complex genre to produce. This is also why a monograph--a sustained, complex argument--is the final writing task you'll face as a graduate student/early-career faculty member.)
* Be reflective about how each dimension of the writing task fits in with other elements. You can only focus on one task at a time, but metacognition and reflection WORK; keep a sense of the whole task as you work on each element. (This is why revision is the longest, most complex step--you are addressing new tasks while trying not to mess up the stuff you've already done)
* Pay attention to HOW the writers you read accomplish the writing tasks they attempt--form, structure, etc.
* And most importantly: Write a lot and get close, serious feedback on your writing